Method of and apparatus for standardizing carbon dioxide gaseous mixtures



Oct. 25, 1932. D. H. KILLEFFER 1,883,941

METHOD OF AND APPARATUS FOR STANDARDIZING CARBON DIOXIDE GASEOUS MIXTURES Filedneo. s1. 195o Patented. 9ct. 25, 1932 Urrea STATES PATENT OFFICE l DAVID H. KILLEFFER, OF YONKERS, NEW YORK, .ASSIGNOR T0 DRYICE EQUIPMENT CORPORATION, OF NEW' YORK, N. Y., A CORPORATION OF DELAWARE METHOD 0F APPARATUS FOR STANDARDIZING CARBON DIOXIIIE GASEOUS MIXTURES r Application tiled December 31, 1930. Serial No. 505,708.

My present invention is related to that of companion application of even date. Ser. No. 505,707, in so much as' it is shown as embodied inl apparatus ofthe type in which the heavy gas evaporating from the solid carbon dioxide is discharged into the atmosphere of the refrigerated space. As explained in said application, certain of the products to be refrigerated are not affected l@ by the gas and others can be easily protected from it, While there are still others not easily protected and which may be seriously dam- Y aged thereby. As concerns the latter class,

it has been proposed to eliminate the dfliculty entirely by discharging all the gas outside of the' refrigerated space; also it has been proposed to allow the gas to leak out rapidly enough to avoid production ot dangerous concentrations. However, experience shows that many products likely to be injured by an atmosphere containing too great percentage of carbon dioxide gas, may be greatly beneted by an atmosphere of air containing only certain limited percentages of the gas; for example, certain vegetables, cut flowers, fruits and the like; and one object of my invention is to provide simple, reliable means for automatically controlling the composition so as to maintain proportions suitable fdr the atmosphere of the particular product to be preserved thereby.

In practice, such control is likely to be p complicated and rendered uncertain by varying internal or external pressures, specific gravity of the gaseous mixture, etc. Such variations tend to produce relatively large volume flow through all ordinary leaks or vents, all gases flowing together in the same direction, either in or out, according to the direction of the pressure. Moreover, differences y, in weight between air 'and carbon dioxide gas, tend to produce gravity outflow of the heavy carbon dioxide gas through low level leaks, thereby'causing inflow of air through higher level leaks.

While these effects may be minimized,v by making the container gas-tight, my invention contemplates employment of a control device that is standardized to a predetermined percentage of carbon dioxide-air mixture and responsive to changes of percentages in the atmosphere of the container and operating to correct any variation from the standard. Preferably, it operates by turning on a carbon dioxide gas supply when the mixture becomes too dilute, but it could be used to turn on an air supply when the apparatus is designed to have a normal tendency to over-richness of gas content.

Preferably, a normal tendency to overdilution is established by providing air inlet and gas outlet means, operating by diffusion of the gases so that different gases How simultaneously in opposite directions, through the same passages, at rates determined by their densities. The exterior air being always practically pure and hence lighter than the internal air-gas mixtures, will diffuse into the container faster than the gas diii'uses outward. For this purpose, I may employ a porous septum having one surface exposed to the air and the other surface exposed to the carbon dioxide gas. In the case of airgas mixtures, the rate will depend upon the average densities of the respective mixtures on opposite sides of the septum. That is to say, other things being equal the rate of passage of air on'one side of the septum into a fifty-titty solution of gas and air on the other side of the septum, will be one-half the rate said pores would pass if the gas were ure.

The difference in functioning between a pore andan Ordinar leak depends on the diilerences in their minimum diameters, that of the pore being very small as compared. with that of the leak. A pin' hole or other passage large enough to be plainly visible will function as a leak rather than as a pore.`

Pores small enough for the purpose are such as exist in ordinary paper. Newspaper is especially porous because it has a minimum amount of binder. Pasteboard contains a greater percentage of binder, but is still very porous, and ordinary corrugated paperboard containing only the ordinary percentage of ordinary binder, is amply porous for most purposes. Dry animal membranes, some kinds of parchment, leather, etc., may also be employed. Where a rigid septum is desired either for structural reasons or to `withstand gas pressures, thin, unglazed porcelain, clay or plaster of Paris slabs may be employed.

The volumes, per unitvtime, of the gases transferred by diusion through the pores will depend on the area, thickness and porosity of the septum, and for purposes of my present invention, the intake of air and output of gas need not be greater than necessary to ensure reasonably prompt dilution of the internal atmosphere when it becomes over-rich in gas. j

rl`he automatically responsive control device which l utilizeforcontrolling inflow of the corrective supply of gas, that is, carbon dioxide if the container tends to overdilution, or air if it tends to over-richness, may be of conventional construction so far as concerns lthe mechanism for turning on and oit the supply, an electric contact make and break operating to control a simple solenoidal valve motor being shown in the present case. 'lhe standardizing sensitive element that causes the make and break consists. of a suitable vessel or container for a gaseous mixture of the same percentage composition as' it is desired to maintainl Within the refrigerated space. rlhe volu-me of gaseous mxture in this container is increased and decreased by transfer of carbon dioxide gas through a septum Which has the peculiar quality of passing carbon dioxide freely, While at the same time being substantially rimpervious to air and moisture. lVhen the concentration of carbon dioxide in contact With the exterior surface of the septum isy greater than the content of the vstandard mixture in contact With the inner face of the septum, the exterior surface absorbs car bon dioxide, the latter going into solution in the material of the septum, diffusing through the same, and being dissolved out again in the more dilute mixture Within the device. Conversely, When the primary mixture Within the device is richer than the exterior mixture, the carbon dioxide dissolves in the other direction and passes to the exterior. Thusthe amount and consequently the pressure of the gas Within the control device increases when the atmosphere to be controlled is too rich in carbon dioxide and decreases when it becomes too dilute in carbon dioxide, as comparedwith the standard percentage of the primary mixture. .These changes in pressure may be utilized in any desired way to turn on a gas supply when,

the exterior mixture is too dilute and to turn it ofi' again when the exterior mixture is too rich. A very thin diaphragm of very pure rubber is phenomenally suitable for thus dissolving and transferring the carbon dioxide gaswithout passing nitrogen or oxygen or moisture of the external atmosphere, at least not quantities or in Ways capable of having tasas-1i any practical eifect on the make 'and break of the control circuit. Other materials in which carbon dioxide gas is highly soluble may be employed for this purpose.

The above and other features of my invenr.

tion may be more fully understood from the following description in connection with the accompanying drawing, in which Fig. 1 is a vertical sectional elevation showing more or less diagrammatically a chamt. ber and automatic means for controlling the percentage of carbon dioxidegas in the atmosphere thereof;

F ig. 2 is an enlarged detail vertical sectional view showing a modified forni of auto- For most purposes, an inner Wall or layer 2, 1

may be provided for structural strength, usually of heat insulating material, because the diluted carbon dioxide gas mixtures are as a rule more beneficial to fruits, cut flowers and the like, when the chamber is moderately refrigerated; temperatures of 40 to 50 F. being desirable in many cases. vWhere the con tainer is air-tight, some form of pressure relief outlet as vent 3, may be arranged to prevent undue pressures of accumulated` gas Within the chamber.

In the present case, the source of the carbon dioxide gas is shown as solid carbon dioxide 4, enclosed in a container which may be in the form of a box 5, of balsa Wood or other insulating material. This box may be charged with solid carbon dioxide through openings which are normally closed by inner cover 7 and outer cover 8. rThe structure maybe designed in anyof the Ways Well knoWn'in the art for.v insuring heat absorption and gas evolution by the solid carbon dioxide at rates required to maintain desired temperatures Withinthe refrigerator 2, and the gas may be causedto flow through ducts which may be inner and outer Walls interposed as insulation to protect the chamber from inleak of heat. the important point being that the gas shall not be discharged into the chamberexcept when the automatically operated control valve is open. Normally, the gas flows through conduit 9 and standpipe 10 into the outer air; but When valve 11 is open, it flows through pipe 1Q into the atmosphere of the refrigerated space. rlhus the design of the parts is such that an ample supply of carbon dioxide gas is always available through valve 1l to increase the gas content of the atmosphere in said space.

While leaks may be employed in various Ways to establish a condition Where said atmosphere Will tend to become too diluted, l prefer to employ a porous septum between the outer air and said atmosphere, as indicated at 13, it being understood that the insulation 2 is fibrous like kapok or at least is not dense enough to prevent diffusion of carbon dioxide outward from the atmosphere within the re-' frigerator and of air inward from the exterior atmosphere. The porous septum 13 may be a. sheet of ordinary permeable pasteboard or corrugated board or unglazed porcelain or, in fact, any of the porous materials hereinbefore mentioned. While the area, thickness and diffusion capacity of such a septum may be designed with reference to the rest of the apparatus., to maintain a normal diffusi on rate suitable for diluting the inner atmosphere with reasonable promptness under average' conditions, I prefer to employ a slide 13m, whereby more or less of the outer surface may be cut off from access of the external air, whereby the dilution rate may be adjusted, as desired. The vent 3, employed to prevent excessive internal pressures, may be formed with a. reverse bend as shown, operatingr as a valve on the principle of a plumbers trap. The Huid affording the seal may be a liquid or may be simply the heavy gas or air-gas mixture flowing from the. interior. In certain cases, the intake of this vent may be extended rmany desired distance toward the bottom of the space where the mixture is likely to be richer in carbonV dioxide gas.

Matters being thus arranged so that the atmosphere of the refrigerated space has a normally constant internal pressure, in this case the same as that of the exterior atmosphere, and having a normal tendency to become too dilute, the desired percentages of the mixture will be maintained by the standardized control'device. This, as shown in Fig. 1, may comprise a gas-tight container 14 closed by a gas permeable septum 15 which may be thin pure rubber, preferably sustained against substantial bulging either inward or outward by wire screens 16, 17. This cover section may be secured gas-tight by application of a rubber solution with or without the aid of mechanical clamping means. The container 14 communicates through pipe 18 with a casing 19 closed gas-tight by a iiexible metal diaphragm 20.

'I he entire space enclosed by parts 14:, 15, 18. 19 and 20, is filled with a standard carbon dioxide gas and air mixture., say 25% gas and 75% air; or whatever other percentage `mixture it is desired to maintain within the atmosphere of container 1. As before explained, the carbon dioxide gas of this standardized mixture will be transferred through the rubber to the. atmosphere of the refrigerated space or .vice versa, according to which atmosphere contains the greater carbon dioxide gas content; and the rate of transfer through the rubber in either direction is proportional to the partial pressure of the carbon dioxide gas moving from higher partial pressurev of the richer mixture toward the lower partial pressure of the more dilute mixture.

As shown in the drawings, the mixture in the refrigerated space may beassumed to be the same or greater than that of the standard atmosphere of the refrigerated space below standard. Thereupon, carbon dioxide gas will dissolve outward through the rubber diaphragm 15, creating a partial vacuum in 14, thereby fiexing diaphragm 20 upward. Such upward motion is utilized in any desired way to open valve 11, allowing the carbon dioxide from the source 4 to How into the atmosphere of the refrigerated space, increasing the carbon dioxide content of the latter. In due course the percentage ofthe latter gas will baisedabove standard,where upon the rubber iaphragm will dissolve and transfer the gas in the opposite direction, to the interior of 14, thereby relieving the vacuum and permitting the diaphragm to return to normal or below normal, according to the amount of gas thus introduced into 14. This reverse motion is utilized to again lclose valve 11.

The valve and valve operating means are diagrammatically indicated in the drawings as including'a switch or contact make and break 21 of circuit 22, serially including battery 23 and a solenoid coil 24 which when energized lifts the plunger 25, thereby lifting the movable member 26 of the valve 11.

The standard mixture in 14 may be produced initially, or may be renewed or changed subsequently, in any desired way. A quantity of accurately proportioned mixture may be prepared, verified by a CO2 analysis indicator and then introduced by removingv sealing plug 27, submerging the device in said mixture until thorough diifusion causes external and internal to become the same, and then re-inserting the said plug 27.

In this connection, it will be understood thatwhile there are great differences in the percentages of the carbon dioxide gas that various perishable products such as fruits and iowers will stand without injury, and also in the percentages that are most beneficial, there are special cases where the maximum beneficial percentage is quite low. Thus, while 80% carbon dioxide may not injure rhubarb, 5.0% may be all that is desirable for oranges, 20% for peaches, 15%'for strawberries, etc. The point is that any desired percentage of gas-air mixture may be attained by the above or any-other equivalent adjustpercentage and pressure4 ment of the effective area of the porous septum and, when necessary, discharge of part of the carbon dioxide gas supply inside the refrigerator. Furthermore, the range between helpful percentages and those that begin to be substantially injurious are so Wide that it is not difficult to get improved results in any apparatus of predetermined, tested design. For testing and standardizing, a carbon dioxide gas analysis indicator may be employed; or, if desired, it may be a permanent part of the equipment.

So far as concerns the above method of making a desired gas-air mixture for the atmosphere of the container 1, it will be evident that any other source of carbon dioxide gas could be substituted for that shown in Fig. 1. rPhat is to say, a box like. 5 could be located outside of the refrigerated space and could be provided with as much insulation as may be necessary to make it yield gas at a desired rate entirely independent of what may be required where it has a refrigerating function inside of the container 1 as shown in the drawings; or a tank of liquid carbon dioxide gas could be used as the source; or any otherv source of carbon dioxide gas, or mixture requiring dilution, may be employed.

As before indicated, the apparatus shown in Fig. 1 could be iliade to regulate the airy gas mixture in any gas-tight container 1 by having an over-supply of carbon dioxide continuously discharged into the container and causing the control device 14 to operate a drain valve or leak in the bottom of the container whereby when the atmosphere is overfich, the drain will be opened, thereby pernitting the heavy internal mixture to iiow out, thereby sucking in an equal amount of air through the high level vent 3 until the dilution has become suiicient to restore 14 to normal, thereby reclosing said drainage valve. A

Various means may be employed for translating the change of volume in a sealedcontainer into motion for controlling opening and closing of valves'at the required times, in accordance -Withlhe above described principles. For instance, in Figj). I have shown a sealed vessel 14a having a rubber or other CO2 solvent diaphragm 15a. This diaphragm may be stretched or held so tightly that the changes of internal pressure would take effeet upon liquid 30 sealing the U-bend 31 of standpipe 32 containinga plunger 33 that will be forced to rise when the internal pressure rises, and fall when said pressure falls, the motion being applied in any desired way to control the valve. l'Io whatever extent the diaphragm itself iexes upward or downward with changing pressures, the motion of the liquid 30 will be 4to that extent reduced. However", convexing and concaving of the diaphragm may be directly utilized, as, for

instance, through rise and fall of a diaphragm i,ess,941

trol the closure of two or more circuits at different positions of its reciprocatory movement.

In all cases, the standard mixture in the controlling device may be given a somewhat different normal internal pressure and a somewhat different normal internal standard mixture to cause the opening or closing of the corrective valve to lag or lead the condition of either of over-dilute or of over-rich mixture in the atmosphere controlled thereby. It will be understood that refrigerator l is provided with openings having air tight closures, not shown, for insertion or removal of perishable products, etc.

I claim 1. A method of refrigerating and controlling the composition of an enclosed atmosf phere of carbon dioxide gas mixed with air by means of solid carbon dioxide, which includes causing the composition and resulting density of the mixture to vary from the standard in the direction of over-dilution; utilizing the over-diluted atmosphere to control inflow of carbon dioxide gas by exposing in said atmosphere a surface of thin rubber septum, causing the solvent activity of said material to vary in Vaccordance with a predetermined standard by maintaining a fixed qualit-ity o f standard cai bon dioxide gas-air mixture in solvent relaton to the other surface `of said septum, thereby causing the carbon dioxide gasto be transferred through the solvent septum in one direction or the other according as the exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture and utilizing such pressure changes to cause supply of carbon dioxide gas to the atmosphere of the container to correct the overdilution.

2. A method of refrigerating and controlling t-he composition of an enclosed atmosphere of carbon dioxide gas mixed with air by means of solid carbon dioxide, which includes causing the composition and resulting density of the mixture to vary from the standard in the direction of over-dilution; utilizing the over-diluted atmosphere to control :'nfiow of carbon dioxide gas by exposing in said atmosphere a surface of a septum of material which is highly solvent for carbon other according asthe exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said.

standardized gas mixture and utilizing such pressure changes to cause supply of carbon dioxide gas to the atmosphere of the container to correct the over-dilution.

3. A method of refrigeratin'g by means of solid carbon dioxide and controlling a standard composition of an enclosed atmosphere i of carbon dioxide gas mixed with lighter gases, which includes causing the composition and resulting density of the mixture to vary from the standard in a desired predetermined direction, by operating differentially to remove one or more of the constituents more. than the other or others, and restoring the mixture to standard by controlled supply of the constituent gas that tends toward a minimum by exposing in said atmosphere a surface of a septum of material which is highly solvent for carbon dioxide gas; causing its solvent activity to vary in accordance with a. predetermined standard by maintaining a fixed quantity of standardized carbon d-ioxide gas mixture in active relation to the other surface of said septum, thereby causing the carbon dioxide gas to be transferred through the solvent septum in one direction or the other according as the exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture and utilizing such pressure changes to control supply of the diminishing constituent in the atmosphere of the container.

4. A method of refrigerating andcontrolling the composition of an enclosed atmoshere of carbon dioxide gas mixed with air y means of solid carbon dioxide, which includes causing the composition and resulting density of the mixture to tend toward overdilution by diffusion through a porous septum having one surface in contact with said mixture and the other in contact with air; restoring the thus diluted mixture to standard by supply of carbon dioxide gas; controlling said supply by exposing in said atmosphere a surface of the thin septum of rubber, causing the solvent action of said septum y to vary in accordance with a predetermined standard by maintaining a fixed quantity of standard carbon dioxide gas-air mixture in solvent relation to the other surface of said septum, thereby causing the carbon dioxide gas to be transferred through the solvent septum in one direction or the other according as the exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture and utilizing decreases ofsuch pressure to supply clrbon dioxide gas in the over-diluted atmosp ere.

5. A method of refrigerating by means of solid carbon dioxide and of causing the composition and resulting density of a carbon dioxide gas-air mixture to indicate variations from a predetermined standard, which meth-l od includes exposing to said mixture a surface of a septum of material which is highly solvent for carbon dioxide gas; causing its solvent activity to vary in accordance with a predetermined standard by maintaining a fixed lquantity of standardized carbon dioxide gas mixture in active relation to the other surface of said septum, thereby causing carbon dioxide gas to be transferred through the solvent septum in one direction or theother according as the exterior or interior percentages of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture and utilizing such pressure changes to produce motion of a mechanically movable element.

6. A container refrigerated by means of solid carbon dioxide enclosing an atmosphere of carbon dioxide gas mixed with air, designed and operating to cause the composition and resulting density of the mixture to vary from the standard in the direction of overdilution; in combination with means for supplying carbon dioxide gas and means for utilizing the over-diluted atmosphere to `control inioW of carbon dioxide gas from said source, said meansy including a thin rubber septum having one surface exposed to said atmosphere, a sealed container maintaining a fixed quantity of standard carbon dioxide gas-air mixture in solvent relation to the other surface of said septum, thereby causing the carbon dioxide gas to be transferred through the solvent septum in one direction or the other according as the exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture and means for utilizing such pressure changes to turn on said means for supplying carbon dioxide gasto the atmosphere of the container.

A container refrigerated by means of solid carbon dioxide enclosing an latmosphere of carbon rdioxide gas mixed W1th air, designed and operating to cause the composition and resulting density of the mixture to vary from the standard in the direction of over-dilution; in combination with means for supplying carbon/dioxide gas and means for utilizing the over-diluted atmosphere to control inflow of carbon dioxide gas from said source, said means including a septum of material which is highly solvent for carbon dioxide gas, having one surface exposed to said atmosphere, a sealed container maintaining a fixed quantity of standard carbon dioxide air-gas mixturein solvent relation to the other surface of said septum, thereby causing the carbon dioxide gas to be transferred throu h the solvent septum in one directionor Y the ot er according as the exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture; `and means for utilizing such pressure changes to turn on said means for supplying carbon dioxide gas to the atmosphere of the container.

8. A container refrigerated by means of solid carbon dioxide enclosing an atmosphere of carbon dioxide gas mixed with lighter gases, designed and operating to cause Jthe composition and resulting density of the mixture to vary from the standard in a desired predetermined direction, by operating differentially to remove one or more of the constituents more than the other or others, in combination with a source of supply of the constituent gas that tends toward a minimum and means for controlling it, including a septum of material which is highly solvent for carbon dioxide gas having one surface exposed to said mixture, a sealed container maintaining a fixed quantity of standardized carbon dioxide gas mixture in active relation to the other surface of said septum, thereby causing the carbon dioxide gas to be transferred through the solvent septum in one direction or the other according as the exterior or interior percentage of the carbon dioxide gas/fis the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture; and means for utilizing such pressure changes to turn on or 'off the source of supply of the diminishing constituent in the atmosphere of the container.

9. A container refrigerated by means of solid carbon dioxide'enclosing an atmosphere of carbon dioxide gas mixed'Wit-h air, means for causing the composition and resulting density ofthe mixture'to tend toward overdilution, said means including a porous diffusion septum having one surface in contact With said mixture and the other in contact with air; in combination with a source of supply of carbon dioxide gas and means for controlling said supply, said control means including a thin rubber septum having one surface in absorbent relation to said mixture and'means for maintaining a fixed quantity of standard carbon dioxide gas-air-mixture in solvent relation to the other surface of said septum, thereby causing the carbon dioxide gas to be transferred through the solvent aeeaeei septum in one direction or the other according as the exterior or interior percentage of the carbon dioxide gas is the greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture; and means for utilizing decreases of such pressure to turn on the supply of carbon dioxide gas to the over-diluted atmosphere.

10. Means for refrigerat-ing by solid carbon dioxide and for causing the composition and resulting density of a carbon dioxide gas-air mixture to indicate variations from a predetermined standard, said means including a septum of material which is highly solvent for carbon dioxide gas, having one surface exposed to saidmixture, and means for maintaining a. lixed quantity of standardized carbon dioxide gas-air. mixture in active relation to the other surface of said septum, to be transferred through the solvent septum in one direction or the other according as the exterior or inter'r percentages of the carbon dioxide gas is t e greater, thereby producing corelative changes of amount and pressure of said standardized gas mixture; and meansl utilizing such pressure changes to produce motion of a mechanically movable l element.

Signed at New York in the countyv of New York and State of New York this 30th day of December, A. D. 1930.

DAVID H. KILLEFFER.

thereby causing carbon dioxide gas 

